Work-head with automatic motions controls

ABSTRACT

56. AUTOMATICALLY CONTROLLED APPARATUS, INCLUDING A WORK DEVICE, MEANS FOR TRANSPORTING SAID WORK DEVICE THROUGH THREE-DIMENSIONAL RANGES OF POSITIONS, AND CONTROL MEANS FOR SAID WORK DEVICE AND SAID TRANSPORTING MEANS, SAID CONTROL MEANS INCLUDING A FIRST SOURCE OF CONTROL INFORMATION FOR DETERMINING A PRESCRIBED PROGRAM OF MOTIONS OF SAID WORK DEVICE IN THREE-DIMENSIONAL SPACE, A FURTHER SOURCE OF CONTROL INFORMATION INDEPENDENT OF SAID TRANSPORTING MEANS FOR GENERATING, DURING OPERATION OF SAID FIRST SOURCE, OFFSET INFORMATION THAT VARIES IN THE COURSE OF THE PROGRAM PROVIDED BY SAID FIRST SOURCE OF CONTROL INFORMATION, AND MEANS COMBINING AND RESPONSIVE JOINTLY TO SAID FIRST AND FURTHER SOURCES OF CONTROL INFORMATION FOR CONTROLLING SAID TRANSPORTING MEANS TO EXECUTE SAID PRESCRIBED PROGRAM OF MOTIONS MODIFIED BY THE GENERATED OFFSET INFORMATION.

June 3, 1975 I 5. c. DEVOL EI'AL Re. 28,437

WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS Original Filed July 30, 1968 6Sheets-Sheet 1 m an,

Juno 3, 1915 I c, DEVQL h TAL Re. 28,437

WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS Original Filed July 50, 1968 6Sheets-Sheet 4 lllllhlll'i'mllllll 2/4 2/0 m 244 245 WORK-HEAD WITHAUTOMATIC MOTIONS CONTROLS Original Filed July so, 1968 G. C. DEVOL ETAL Juno 3, 1975 6 Sheets-Sheet 5 i I I -JEA' WORK-HEAD WITH AUTOMATICMOTIONS CONTROLS Original Filed July 30, 1968 June 3, 1975 a. c. DEVOLETAL 6 Sheets-Sheet 6 m 0 Z 8 0 Z 4 x a 2 a J u 8 3 J a a MW 6 3 22 a aE- 3 6 |!..l 7 2 F2 a 5 7 2 3 3 5 a 8 3 M 5 3 5 United States Patent;

e. 28,437 Reissued June 3, 1975 28,437 WORK-HEAD WITH AUTOMATIC MOTIONSCONTROLS George C. Devol, 990 Ridgefield Road, Wilton, Conn. 06897, andPaul S. Martin, 189-54 43 Road, Flushing, N.Y. 11358 Original No.3,543,910, dated Dec. 1, 1970, Ser. No. 748,703, July 30, 1968.Application for reissue Nov. 30, 1972, Ser. No. 310,769

Int. Cl. B65g 47/08 US. Cl. 198-34 68 Claims Nlatter enclosed in heavybrackets If appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE The disclosed apparatus has a work-headmovable in program-controlled three-dimensional paths by an extendableand retractable arm that is movable through angles both in azimuth andelevation. The Work-head may be any of various tools. As shown, thework-head has article gripping jaws. The work-head is also operableabout horizontal and vertical axes at the end of the arm. Each motion isproduced by a respective drive unit, especially a hydraulic actuator,and has a corresponding control. Inverse angular controls can be used toenforce equal and opposite angular movements of the work-head about itsaxes corresponding to the angular motions of the arm in elevation andazimuth.

In one form of the apparatus, the control information is supplieddirectly to the respective polar-coordinate controls, in polar form. Inanother form of the apparatus, the control information is supplied inrectangular coordinates and controls the operation of a manipulatingunit having respective parts movable in mutually perpendicular directions, and the manipulating unit operates a lever that is movable inelevation and azimuth and operable lengthwise by elongation andcontraction, and in turn, the lever acts as a converter or as part of aconverter in operating the polar-coordinate controls of the work-headoperating apparatus.

There is a linear-motion control in both forms of apparatus additionalto the controls already mentioned for producing a control eifect tocause straight-line motion of the work-head in a direction that involveslengthwise and angular motion of the arm that carries the work-head.Information can be supplied to this linear-motion control in increments,as in pallet loading; or it can be supplied continuously to enable thework-head to carry out a program of control informationin relation to awork space on a continuous conveyor. There is a converter in thepolar-coordinate apparatus that responds to the linearmotion control andprovides polar-coordinate output for introducing off-set input into thepolar-coordinate controls that otherwise respond to the polar coordinatecontrol information. In the rectangular-coordinate apparatus, thelinear-motion control introduces an off-set in the manipulating unitthat responds otherwise to its input con trol information.

This application is a reissue of Pat. No. 3,543,910 which matured fromapplication Ser. No. 748,703 filed July 10, 1968.

The present invention relates to apparatus in which a Work head isoperable automatically to execute a sequence of motions. The work headmay assume various forms, such as a drill, or a paint-spray gun, or anassembling tool, or jaws of a resistance welder; but the features of thei.nvention are described below primarily in relation to article-transfer-apparatus in which the work head has an article gripper.

Apparatus of this type has been developed for operatlon under programcontrol to execute prescribed sequences of operation. The apparatus isvery flexible, since it can be adapted to new uses merely by developinga new program. Typically it includes a work head that is carried throughspace in a primary three-dimensional pattern of motions and the Workhead itself is operable in secondary motions to assume various attitudesas it is carried through its pattern of motions. Examples of suchapparatus are shown in US. patents issued to G. C. Devol, Nos. 2,988,-237, 3,251,483, 3,279,624 and 3,306,471.

A particularly useful form of construction involves an arm that carriesthe work head where the arm is operable about at least one axis. In acommercial program-controlled article-transfer apparatus, there arethree primary motions of the arm, about vertical and horizontal axes,and telescopic elongation and retraction of the arm; and in addition aunit carried by the arm is capable of moving the work head in what maybe called secondary motions, such as a wrist-bend motion. In anapplication filed concurrently herewith by George C. Devol, one of theapplicants herein, a related improvement is disclosed, providing forautomatic correlation of a work head pivotally carried by an arm that isitself operable about a parallel pivot, to maintain constant aim of thework head.

Because of the primary angular motions involved in that type ofapparatus, the straight-line motion of the work head in any onedirection involves a certain amount of complexity. The problems arefurther complicated where there is a sequence of positions to which thework head is to move which are related to each other in a basicallyrectangular-coordinate system. Each required motion of the head along aline parallel to an axis in a rectangular coordinate system must includecontrol constituents that take into account the angular motions of thearm and the armlength change. For example, an article transfer apparatusmay be applied to the loading or unloading of pallets with articles in arectangular pattern of rows, columns and layers. In another example, awork head may be required to keep up with one section of a conveyormoving along a straight line. The latter problem is dealt with in onemanner in Pat. No. 3,283,918 to G. C. Devol, wherein theprogram-controlled apparatus is bodily shifted in synchronized motionwith one segment after another of the conveyor to execute its programcycle.

Accordingly, an object of the present invention resides in providingmotion-control apparatus that responds to linear control information forcontrolling a Work head carrying an arm that is movable about at leastone axis and wherein the arm is operable lengthwise to extend andretract the work head, and more particularly wherein the arm is movableabout two mutually perpendicular axes.

A further object of the invention resides in providing motion controlapparatus that is adapted to respond to instructions given in terms ofrectangular coordinates in a plane or in space for controlling themotions of an arm that moves a work head to various extended andretracted positions and about at' least one axis, and more particularlywhere the apparatus is one that has an arm operable about mutuallyperpendicular axes.

As indicated above, program-controlled apparatus has heretofore beenavailable commercially that has an arm operable about horizontal andvertical axes and carries a work head capable of angular motion on thearm. The unit carried by the arms has been capable of executing awrist-hen motion. The Work head itself has been capable of twist motion.

An object of this invention resides in providing such apparatus withincreased capability, by adding a further wrist-bend motions aboutmutually perpendicular axes.

The twist motion'may be retained if desired.

An object related to theforegoing feature resides in providing means forcoordinating the operations of a work head through changes in bothazimuth and elevation angles in' relation to a supporting arm withchanges in the angles of azimuth and elevation of the arm formaintaining constant aim or attitude of the work head as it is bodilytransported by its'supportingla'rm through complex motions in space.

A still further object-resides in providing a means for modifying theoperation of apparatus having an arm movable through an angle about anaxis and carrying a work head to extended and retracted positions, andWherein the worlc'head itself is operable about a parallel axis, so thatthe angle of the arm and its length change, and the angle of the workhead relative to the arm changes, so as-to move the Work head along astraight-line path, to maintain a constant relationhip of the work'hea'dwith a point in. space that is moving along a straight line. Forexample, the point may be'identified with-a discrete portion of aconveyor moving along a straight-line path.

A further object of this invention resides inmodifying the operation ofapparatus of such construction to execute a program of operationestablished initially in a stationarycspace", where the space is thenset in motion along a line passing the apparatus.

A further object resides in adapting apparatus of the type having an armthat can extend and retract a work head and Where the arm is operablethrough-angles of azimuth and elevation, and where the work head isoperable relative to the arm through angles crazimuth and elevation, sothat the work head can maintain a constant relationship with a point inspace that moves along a straight line. A still further object is toadapt such apparatus to execute a program of operations in relation to asegment of a conveyor in motion where the program was established inrelation to a stationary volume or space.

The cooperation of program-controlled apparatus of the constructionconsidered above with a conveyor is but one example of automaticoperation under a program control, modified by a second source ofcontrol informationpMore generally expressed, an object of thepresent-invention resides in providing apparatus normally operable undercontrol of a main source of control information to move a work headthrough prescribed patterns of motion, with off-set control means and asupplementary source of offset control information to modify the patternof motions that would otherwise be executed under control of the mainsource of control information.

Another object related to the foregoing resides in adapting suchapparatus to alternate operation with and without control by the ofi-setsource of information. Such a situation arises (for example) where anarticle transfer unit is to transfer a seriesof articles from astationary supply point or a pattern of stationary supply points to apoint or a series of spaced-apart points all of which are identified inthe program of the apparatus, butwhere the delivery point or points areset in motion on a conveyor. The article holder operates solely undercontrol of the program in approaching the stationary supply point timeafter time, but it moves to'a progressively advancing point or toprogressively advancing mutually separateddelivery points in alternationwith its motions to the supply point or points under an off-set controlthat represents the .motion of the conveyor, and where the oif-setcontrol is alternately in effect and removed from effect.

"The foregoing and other objects, advantages and features are realizedin the illustrative apparatus described below and shown in theaccompanying drawings that form part of the disclosure of suchapparatus. Generally, two embodiments are shown. A basic structureuseful in both embodiments includes an arm that is carried on a rotata-"ble post and pivoted on the post about a transverse axis to'r'aiseandower=a ork-head'carriecl'byth arm/That two axes are involved is ofdistinct advantage but broader aspects of the invention apply toa'structure' in which the arm is bodily moved, linearly, for raising andlowering the work head. The work head is carried by the arm forcorresponding movements about horizontal and vertical angles of tilt andswing, these being the motions referred to above as doublewrist bends.The 'work head itself may be arrang'd to rotate about its axis 'and itmay have its own further adjustments or controlled ,actuato'rs, as maybe needed. In the illustrative structure, the tilt angle and theswingangle are coordinated in several ways withrthe angles of elevation ofthe arm and turn of the arm-supporting post. v 4

The control apparatus for. such a structure for adapting it to respondto linear-motion control information is described in connection with twoillustrative embodiments showninthe drawings. Each includes a converter"that responds to linear control operation and provides output controlfor .the required motions, of the arm thatcarries the work head. 1

1' The converter includes a. lever-having the same motioncapabilities-as the arm that carries the work-head; The

lever operates servo-master controls, while the actuators of the arm inits various motions are controlled bywhat mayxbe considered servo slaveunits. The master and slave controls are coupled to each othervariously, e.g., electrically and electromechanically. I

i In one of these embodiments, the converter responds tothree-dimensional rectangular-coordinate control information. Thisinformation may come from various sources, as from a recorded program,or a computer, or both. In one of its coordinates there is an off-setinput of linear control, from the conveyor. The pattern of operations ofthe work head in space is controlled by information from the main sourceof control information, here the program drum, and the operations thenensue in relation to a stationary space. The identical motions areexecuted in relation to a moving space: as a result ofoff-set-information supplied to the converter-by a servo link to theconveyor. The converter automatically changes the angles of elevationand azimuth ofthe arm, and its length, asneeded, either for keeping thework head in constant cooperation witha pointin space that moves withthe conveyor, of for enabling the-work head :to keep pacewiththe-advancihg pattern of points that are involved in the program.

In a second embodiment the program control information is provideddirectly toeach control for the actuators that tilt, swing and extendthe arm which carries the work head. Aconverter is provided that-has alinear input control operated by a servo link to a conveyor, and thelever of the converter operates controls that introduce an appropriateoff-set into each of the actuator'controls of the arm for keeping theWork head on the arm in step with a point or a pattern of points on theconveyor.

The nature of the invention in its various aspects is more readilyunderstood andappreciated. from the following detailed description ofthe illustrative apparatus shown in the accompanying drawings.

In the drawings: t a

FIG. 1 is a lateral elevation of an article-handling apparatus shownpartly in cross-section and showing in broken lines a position assumedby one of its parts in the course of operation;

FIG. 1A is an enlarged cross-section of part of the apparatus of FIG. 1as viewed from the plane 1A1A in FIG 1;

FIG; 2 is a top plan view of theapparatus of FIG. 1, showing in brokenlines a position assumed-by part of the apparatus in the course of itsoperation;

"FIG. 2A is a fragmentary View of aportion oyFlG. 2, drawn-to largersc'ale," i

FIG; 3 "is an enlarged lateral cross-section of a detail in FIG. I,viewed from a vertical plane atright angles to FIG. 1;

FIG 4 is an enlarged view of part of the control structure in units 86and 88 of FIG. 2;

FIGS. 4A, 4B and 4C are modifications of the control apparatus of FIG.4;

FIG. 5 is a block diagram showing the coordinating and program-controlapparatus for the apparatus of FIGS. 1 and 2;

FIG. 6 is a somewhat diagrammatic lateral elevation of the apparatus ofFIGS. 1-4, modified to include further features of the invention;

FIG. 6A is a diagram illustrating a manner of operation of the apparatusof FIG. 6;

FIG. 7 is a plan view, partly in cross-section, of the converter in FIG.6;

FIG. 8 is an end view of the converter of FIG. 7;

FIG. 9 is a top plan view of a detail of the converter of FIG. 8;

FIG. 10 is a perspective of a pallet loaded with cartons which theapparatus of FIGS. 6-9 is useful;

FIG. 11 is a diagram of a portion of the control mechanism useful in theembodiment of FIG. 7 to enable alternate operation of the apparatus withoff-set for synchronized operation with the conveyor and for eliminationof such oif-set;

FIG. 12 is a lateral somewhat diagrammatic view of apparatus as shown inFIGS. 14 modified to include certain additional features of theinvention;

FIG. 12A is a diagram illustrating the operation of the apparatus ofFIG. 12;

FIG. 13 is the elevation of part of the apparatus in FIG. 12, drawn tosomewhat larger scale;

FIG. 14 is a plan cross-section of the apparatus in FIG. 13 as viewedfrom the section line 14-14;

FIG. 15 is a fragmentary perspective of the apparatus of FIGS. 13 and14, in a modified operating state; and

FIG. 16 is a detail of a portion of the control apparatus linking theconverter of FIGS. 13-15 with the rest of the apparatus in FIG. 12.

Referring now to FIGS. 1, 1A, 2 and 2A, an articletransfer apparatus 10is shown including a base 12, a vertical post 14, and an arm 16 carryinghead unit 18. Base 12 contains a drive motor 20 which operates throughchains 22 to rotate the center shaft 24 of post 14 about its verticalaxis. Shaft 24 rotates within a stationary sleeve 26 on base 12, and issupported for rotation by bearings 28 and 30. A shell 32 is secured toshaft 24 above bearing 28, and rotates with the shaft.

Hydraulic actuator 34 (which may be simply a piston Operating in acylinder with hydraulic lines to its extremities) has a pivotalconnection 34a to rotary shell 32, and actuator 34 is connected by rod34b to arm 16. By proper control of the pressure supply of hydraulicfluid to the respective ends of actuator 34, rod 34b will elevate orlower arm 16 about its pivot 16a, as desired, or hold the arm at anyangle of elevation.

Ann 16 contains hydraulic actuator 38 comprising pistonrod 38a andpiston 38b, the cylinder in which piston 38b works being secured to arm16 and rod 38a being secured to head unit 18. Radial motion of head unit18 is controlled by admitting hydraulic fluid under pressure to theappropriate side of piston 38b, discharging fluid from the other side ofthe piston. Two tubes 36a and 36b are telescopically received in tubes36c and 36d and support head unit 18. Shafts in tubes 36a and 36b havetelescopic splined connections to drive shafts 50' and 68, respectively.These two telescopic drive shafts cause a swinging motion of work head18a about the axis of shaft 18d and tilting motion about the horizontalaxis of shaft 18c. These axes intersect with each other at a point alongthe axis of rod 38a which may be called the longitudinal axis of arm 16.The axis of rod 38a passes through the axis of pivot 16a, which is thepivotal axis of arm 16. The telescopic shafts maintain the describeddrive connections throughout the range of radial motion of head unit 18produced by actuator 38. Shaft 18c remains horizontal and parallel 6 topivot 16a. Shaft 18d can tilt, but it can also be made vertical andparallel to post 14 despite sloping positions of arm 16.

Horizontal shaft 18c has its extremities in bearings in U-shaped headframe 18b and is rotated by the shaft in tube 36a via bevel gears 40.Shaft 18d operates in tube 18f that is united to shaft 180. Rotation ofshaft 18c about its horizontal axis causes tilting of shaft 18d.

The drive shaft in tube 36b operates bevel gear 42 for rotating a bevelgear unit comprising bevel gears 44a and 44b united to the ends of asleeve 44d that forms a bearing on shaft 18c. Bevel gear 440 meshes withbevel gear 44b, and because gear 44c is fixed to shaft 18d, rotation ofthe drive shaft in tube 36b causes swinging of work head 18a about itsshaft 18d.

A yoke 18a is secured to the ends of shaft 18d and to gear 44c. Yoke 18eswings through a large arc and, if necessary, yoke 18e may be made largeenough to swing about the gear-containing portion of head unit 18. Atthe end of yoke 18c remote from arm 16 there is a drive unit 46 carryingarticle-gripping jaws 48. Drive unit 46 can be arranged to rotate jaws48 about an axis passing through the intersection of the axes of shafts18c and 18d. Unit 46 contains suitable means (not shown) for operat ingthe jaws to grip and release an article.

When equipped with jaws 48, apparatus 10 is operable for transferringarticles from place to place as desired. laws 48 may be replaced by asuction cup as another form of article gripper. Other devices such as adrill, a pair of welding jaws, and other work devices may be mounted onunit 46 in place of jaws 48. Still further, unit 46 may itself contain adriving element for shifting jaws 48 or a substitute tool along the axisof rotary drive unit 46. Such endwise motion is useful, for example, forcausing lengthwise drive of a drill carried by unit 46.

The apparatus thus far described involves a number of independentmotions, each of which may be termed a degree of freedom. Post 14 isrotatable by motor 20 about a vertical axis for operating arm 16 throughvarious angles of azimuth. Actuator 34 operates arm 16 through a rangeof angles of elevation. Operation of actuator 38 shifts head 18radially. These may be termed three primary degrees of freedom. Inaddition, the swinging motion of work head 18a about its axis 18d andthe tilting motion of work head 18a about its horizontal axis providetwo secondary degrees of freedom. Rotation of unit 46 about its axisrepresents a sixth degree of freedom. Another degree of freedom would berepresented by the shift of jaws 48 bodily along the axis of unit 46.

The following means is provided for rotating the shaft in tube 36b, inorder to swing yoke 18c about the axis of shaft 18d. Shaft 50 is coupledto gear 42 through differential 79 and shaft 50 via internal telescopicsplined shafts. Shaft 50 is rotated by bevel grears 52 and 54, thelatter gear being operated by dual sprocket 56, chains 58 and by areverse-acting pair of hydraulic actuators 60. Each of these actuatorsprovides a power stroke in the direction to pull the related end ofchain 58, thereby to rotate sprocket 56 and gears 54 and 52.

Gears 40 are driven via splined shafts in arm 16 extending to shaft 68at the opposite end of arm 16. Shaft 68 is rotated by bevel gears 70 and72, a dual sprocket 74, chains 76 and dual hydraulic cylinder actuators78, the construction and operation of which is the same as thatdescribed for hydraulic cylinders 60 and 62 and the parts driventhereby.

Any rotation of shaft 68 causes shaft 18c to rotate about its horizontalaxis and thereby causes shaft 18d to tilt. However, if this occurs at atime when bevel gear 42 is fixed, thereby fixing bevel gears 44a, 44b,and 440, then the tilting of shaft 18d would result in travel of bevelgear 44c about gear 44b, and would inherently cause yoke 18a to swingabout tilting shaft 18d. This is avoided here by providing adifferential gear unit 79 having input couplings from both shaft 68 andshaft 60 and having its output shaft coupled to gear 42. In case shaft68 shouldnot rotate, any rotation of shaft 50 would be transmitted viathe differential gear assembly 79 to gear'42'. This 'shaft e v i aApparatus includes a poweractuator in each degree of freedom, and isprogram-controlled in each degree of freedom. In the form illustrated,"rotatable shaft 24 of' post 14 is' operated bymotor'20 and carries agear 809. that meshes with gear 80b tooperate unit 706; This unitcontains a digital shaft-position encoder or analog-todigital converterand other devices described below. Rotation of shaft 24 by motor ismonitored by the digital encoder, and can be interrupted or otherwisecontrolled by the relationship in effect at any moment between thedigital encoder and a control program. Motor 20 may be stopped when theencoder matches the program code, or the program code can be replaced bythe'nex't code when match occurs, as desired. Similarly, the elevationof arm 16by actuator 34 is' monitored by means of agear sector 92a fixedto arm 16 and operable about pivot 16a. Sector 82a meshes with pinion82b for operatingdefv (5 82c.

This'device (described below in detail) includesa digital encoder. Stillfurther, the radial motion of arm 16 caused by actuator 38 is monitoredby a unit 84 that' con tains a digital encoder. Unit 84 is operated by agear 84a driven by a pinion 84b secured to drum 84c. An internal'wind-upspring is contained in drum 84c, and thisdrurn is ar- Units 86 and 88geared to shafts and 68 similarly contain digital encodersto'rep'resentthe absolute positions or shafts 18c and' 18d about theirrespective axes, for adapting the apparatus to program control. Detailsof these units appear below.

Each of the motions described is ordinarily subject to independentprogram control. However, it is sometimes desirable to link certainmotions. For example, jaws 48 may grip an article in What may be calleda nor'mal attirestore the rotor of synchro transmitter to anormalstarting angular position.

tude, and it may be important for this attitude to be maintaineddespitea change in the angle of elevation of arm 16 to the broken-line position18 in FIG. 1. correspondingly, it may be desirable to maintain theattitude of'an'article in jaws 48 unchanged, despite the swing of arm 16about the vertical axis of post 14 in carrying head 18 to itsbroken-line position 18" (FIG. 2). The axis of unit 46 a Oct-11, 1965,now Patent No. 3,525,094 by G. Leonard. A gear 94 is normally freelyrotatable on shaft 92. A magnetic. clutch 96 has one plate fixed to gear94 and another plate fixed to shaft'92. Theclutch, when energized,couples gear 94 t0 shaft 92. When this occurs, .gear 94 drives pinion98, and rotates a servo master control, for example synchro torquetransmitter 100. When clutch Unit c is like unit 82c, in that unit 80ccontains both a digital encoder and an optionally operative synchrotorque transmitter.

Units 86 and 88 are made alike, for example as shown iHFIG. 4 v

Plate 103 supports analogto-digital encoderll04 of the same constructionas encoder 90, and a servo slave unit such as a synchro torquereceiver108. Encoder 104 is coupled by gearing 105 to one shaft of differentialgearing unit 107. Another shaft of the differential gearing unit"107 isconnected to synchro'receiver-108. The" third shaft 1 12 of thedifferential gearing-unit iscb'nne'cted-lto sprocket '56 or sprocket74,where the unit shown in FIG. 4 is used as unit 86 or 88 in FIGS. 1 and2.

Sodoirg assynchro'receiver 108*is held inwha't-may be calleditszeroposition;the-position of shaft 112 corresponds to the codeoutput'of encoder 104.Rotation ofsynchro receiver- 104 introduces" anoffset irr'that' relationship. The offset angleas measured at shaft 1l2is -madeequ'al and opposite to the .angle through which synchrotransmitter 100 is'operated from the start to the end of' aprogram-controlledangular motion'of arm 16, provided that there is nochange in the value -'a'gainst which encoder'104'is compared 'andmatched. The change thus'introduced means that there is'no longertheoriginal relationship between' the position of the operatedpart oftheapparatus and the value represented by the related encoder. During anoffset operation of this 'type, arm 16 changes'its angle of elevation,but work head 18a remains "parallel to its original position at thestart of the changeof-elevation travel of the arm 16, by reverselychanging its angular relationship to arm 16.

.A. spring mechanism biases servo receiver 108 to a Zero or homeposition. In that s'ta te,.there is an absolute relationship between thecode produced in encoder 104 and the position of the component to, whichthe encoder is geared. Thus, with .servo receiver 108 in its homeposition and with shaft 112 coupled to sprocket 56, the angular positionof work head 18a about shaft 18d is digitally represented by the codeoutput of encoder 104.'This spring mechanism includes a pair oftorsion-spring units 109 and 111 having the outer ends of internal woundleaf springs fixed to their cases and having the inner ends of thesprings fixedto arms 109a and 111a on respective shafts at the centersof the spring cases. In the home position of the servo'recei-ver, arms109a and 111a bear agaiHSL the opposite. faces of fixed stop 113, andthey also bear against opposite sides of I pins 115a and 1151:.projectingfrom gear. 115. Gear 108a ofthe servo receiver 10S meshe withgear 115. I When theservoreceiver is rotated, gear 115 forcibly liftsone of .the arms.,'109a.0r 111a away from stop 103,

andincreases the..,spring tensionofthe relatedspring unit.

$ubsequentlywhemthe servo; receiver is de'energized, the spring resetmeehaiiiSIh described firmly returns the operated arrri 109a'or11lafintocontact with stopl03, thereby restoring the servo receiver 108 to itshomeli position.

;;- A modification of the apparatus of FIG. 4.is.shown in FIG. 4A.Digital encoder 104 vin FIG. 4Af-is shown mounted on plate106, whichalso supports synchro torque receiver 108. Units 104 and Y108 in FlG. 4Ahave input shafts'to differential gearassembly l lO for operating shaft112, as in FIG. 4.,This-.shaft represents vthe shaft of sprocket 56 orsprocket 74 (FIGS. Land 2).

A precise arrangement is provided for returningservo 108. tofzero. Forthis purpose, synchrotorque receiver 108'ope'rates an assembly 114 ofdiscs that are coupled together in the manner of odometer wheels so.that the disc closest to synchro receiver. 108 operates at-,highestspeedand the others are scaled .down toiindex one step for each ten,hundred, and thousand .rotations of the units ,disc 114a. As .shown inbroken lin'e end view in FIG. 4, the discs are generally round but havea flat,

and all of the flats are aligned horizontally when unit 108 is in itsnormal zero position.

Cooperating with all of the discs of assembly 114 is a pair of normallyopen contacts 116 (shown in broken lines 116) that are closed so long asany one of the discs is out of its zero position. Contacts 118 and 120are normally open, and either of these contacts closes when the flatportion of units disc 114a rotates through a significant angle away fromits zero position. The adjustment of contacts 116 in relation tocontacts 118 and 120 is such that, upon rotation of disc 114a in eitherdirection, contacts 116 close after the closing of one of the two pairsof contacts 118 or 120, depending upon the direction of rotation of disc114a.

Closing of' contacts 116 and 120 occurs when disc 114a rotatescounterclockwise, considering the end-view representation 1143. in FIG.4A. When this occurs, power is connected from line 122, contacts 120 andrelay contacts 124a to relay 126 and to terminal 122'. When this occurs,relay 126' is energized and closes its own holding contacts 12Gb whichmaintain relay 126 energized via line 128 so long as contacts 116 remainclosed. When relay 126 has once been energized, its contacts 126a openand thereby break the circuit from contacts 116 via contacts 118 thatmight otherwise be established to relay 124. Consequently, continuedrotation of disc 114a in a counterclockwise direction, ultimatelyallowing contacts 118 to close, would not cause energization of relay124. On the other hand, if disc 114 should rotate clockwise, therebyclosing both contacts 116 and 118 initially, then a series circuit isformed from line 122 through contacts 116 and 126-a to relay 124 andterminal 122'. This has the effect of closing its holding contacts 124b,thereby maintaining relay 124 energized so long as contacts 116 remainclosed. Energization of relay 124 also opens contacts 124a and therebyprevents subsequent energization of relay 126 when contacts 120 closelater in the continued rotation of disc 114-a. Thus, either relay 124 orrelay 126 is energized, depending upon the direction of rotation of disc114a away from its zero position and the selected relay remainsenergized so long as any one of the discs in assembly line 114 is not inits zero position. On the other hand, when all of the discs are restoredto-their zero position by restoring synchro receiver 108, contacts 116open, and then the energizing connection for the holding-contactcircuits is broken and the energized relay is deenergized.

Relay 124 has a pair of contacts 1240 which, when closed, operate areversing relay 130. Normally, reversing switch 130 provides anenergizing connection from a signal source 132 via contacts 134a ofrelay 134 when closed. At that time, and if reversing switch 130 is thenin its normal condition, then synchro receiver 108 rotates in a firstdirection. In case contacts 124c should be closed when closing ofcontacts 134a occurs, then synchro receiver 108 rotates in the oppositedirection.

Relay 134 can be energized by closing its control contacts 138momentarily. When this is done, relay holding contacts 134b are closed,to complete a holding circuit via lead 128 through contacts 116 toenergizing terminal 122. So long as the synchro receiver is in its homeposition, contacts 116 are open and relay holding contacts 134b cannotenergize relay 134.

A further modification of the apparatus of FIG. 4 is shown in FIG. 4B.Here the case 104' of a digital encoder (in all respects like encoder104) has its frame or housing mounted for rotation with shaft 112 thatcorresponds to shaft 112 in FIG. 4. The movable shaft 1400f the encoderis coupled by gears 142 to synchro torque receiver 108 whose case isstationary. Gear 108a couples the synchro torque receiver to gear '115,this being part of a torsion spring restoring mechanism exactly the sameas in FIG. 4.

The operation of the apparatus in FIG. 3 and each of FIGS. 4, 4A and 4Bmay now be described, in their relationship to the equipment of FIGS. 1and 2. The appa- 10 ratus of FIG. 3 is contained in each of units c,and820 of FIG. 1, and any one of the assemblies in FIGS. 4, 4A or 4B iscontained in units 86 and 88. It may be assumed that the apparatus hasbeen programmed so that work head 46 is horizontal and jaws 48 grip anarticlein its horizontal attitude. Shafts 16a and 18c are parallel toeach other. Arm 16 is initially horizontal or at any other angle ofelevation. Let it be assumed further that it. is desired to maintainjaws 48 horizontal despite swinging of arm 16 through a substantialvertical angle for raising or lowering the article. The horizontalattitude of the article shall not change during this operation. (Theassumption that Work head 46 is horizontal is only an example of itspossible attitudes in the ensuing operations.)

At the start of the operation, clutch 96 (FIG. 3) is energized underprogram control. Any rotation of gear sector 82a representing the changein the program-controlled elevation of arm 16 causes rotation of pinion82b and gears 94 and 98 so as to operate synchro transmitter 100. Thishas the effect of correspondingly rotating synchro receiver 108. Aprogram-controlled motion of arm 16 through a vertical angle would causea corresponding angular motion of jaws 48 when there is no change in thecode that is supplied to control the jaws. Stated otherwise, if jaws 48were aligned with arm 16 and if arm 16 changes its angle of elevation,jaws 48 ordinarily move through the same angle, still aligned with arm16assuming the same control code is supplied to the head motion controlat the start and end of this motion. However, rotation of synchroreceiver 108 introduces a dilferential effect between digital encoder104 and the tilt-control drive of head 18a. This causes hydraulicactuator 78 to operate for maintaining encoder 104 in condition to matchthe program instruction. As a result, shaft 112 operates in suchdirection as to compensate for the changed attitude of arm 116 andmaintain constant the attitude of jaws 48 and the article carried bythose jaws.

The same effect is realized in relation to the horizontal swing of arm116 from the initial position in FIG. 2 to that represented by thebroken-line position 18". Consequently, despite controlled motions ofarm 16 in both azimuth and elevation angles, it is possible to maintainconstant the attitude of the article gripped between jaws 48. At thestart of such parallel-motion mode of operation of work head 18, shaft180 is inherently parallel to shaft 16a. Shaft 18d should be madeparallel to post 14 where azimuth parallel-motion operations are to beexecuted. Jaws 48 can be mounted so as to be capable of tilting on workhead 18, if desired, so that requiring shaft 18d to be vertical in theparallel-motion mode of operation is not a serious handicap.

It is important that the initial absolute digital program control overthe positions of shafts 18c and 18dbe restorable, following aparallel-motion mode of operation, to, undo the offsetting effect of thesynchro transmitter and receiver (or other servo master and slave) justdescribed. For this purpose, it is necessary to restore the synchroreceiver -108 to its zero condition, thereby reestablishing the initialrelationship between each encoder 104 in units 86 and 88 and shaft 112.This is done in FIG. 4 and 4B by deenergizing the synchro receiver sothat spring 109 or 111 operates. In FIG. 4A this is done by momentarilyclosing contacts 138, thereby energizing relay 134 and closing contacts134a. This applies a restoring-motion signal to synchro receiver 108,which operates in the correct direction as previously described forrestoring the assembly of discs 114 to the true zero condition. Whenthat condition is reached, contacts 116 open, relay 134 is deenergized,and operation of synchro receiver 108 is arrested. It is also desirableto restore synchro transmitter to its normal angular position. Thisrestoration is effected simply by tension spring 102, clutch 96 beingdeenergized at this time.

The arrangements in FIGS. 4 and 4A involve a differential gear assembly107 or 110. This is a, complication,

but has the advantage of modifying the effect of digital encoder 104without bodily rotating the frame of the encoderjlnasmuch as many wiresare often involved in the typical encoder, fixed mounting of the encoderis an advantage because it avoids the use of troublesome slip rings forproviding connections to the encoder. However, there are some forms ofencoders where this condition is not of controlling importance; and inthat event, the configuration of parts in the encoder and the offsetmeans in FIG. 4B may be desirable. A still further alternative may bedesired, interchanging encoder 104' and synchro torque transmitter 108in FIG. 4B, thereby mounting the housing of the encoder fixedly andmounting the housing of the offset-introducing synchro receiver onrotating shaft 140. This is shown and more fully described in anapplication filed concurrently herewith by George C. Devol.

FIG. 4C shows a still further approach to the problem of achieving aparallel-motion mode of operation, for maintaining constant aim of workhead 18a despite changes in the angle of elevation of arm 16. Identicalapparatus is useful for maintaining constant aim of work head 18adespite angular motion of arm 16 about post 14, where shaft 18d isvertical at the start of the parallelmotion mode of operation. Actuator34 in FIG. 4C is controlled by encoder 90, program input unit 90a, and acomparator 90b in which the difference between the encoder and theprogram instruction is derived. Comparator 90b controls a valve 34a tocause operation of actuator 34 in the appropriate direction independence on the algebraic sign of the difference, and to shut thevalve when the difference reaches zero. This is the normal control meansfor the elevation of arm 16. An example of such control is shown in US.Pat. 2,927,258 issued to B. Lippel. Actuator 60 provides the driveeffort to tilt head 18a. Valve 60a controls actuator 60. Program inputunit 104a supplies the usual input control for the tilt motion of workhead 18a, to be compared with the encoder 104 that monitors the tiltposition. Comparator 104b provides output for controlling the valve 60a.Comparator 104b responds to input values from the encoder and theprogram input unit, and provides an output representing the difference,so as to operate actuator 60 in the appropriate direction and to shutvalve 60a when the input values are alike.

In FIG. 4C, a numerical combining unit 108 is included to introduce aparallel-motion offset, comparable to the effect of synchro receiver108. When switching means 108b is closed, register and [added] adder108' takes the algebraic sum of the output of encoder 104 and thenumerical difference of the number of pulses needed to reduce to zerothe difference between encoder 90 which represents the initial elevationof arm 16 and program unit 90a which represents the final elevation ofarm 16 at the end of the motion to be executed. Adder 108' supplies thisalgebraic sum to comparator 104b with its algebraic sign reversed, to becompared with the program input. Assuming this to be a parallel-motionmode of operation, the program input from unit 104a does not change, andactuator 60 causes an angular tilt motion of work head 18a that is equaland opposite to the change-of-elevation motion of arm 16 to be carriedout or being carried out by actuator 34. Succeeding operations of arm 16by its actuator 34 and of work head 18a by its tilt actuator 60 in theparallel-motion mode are carried out in the same way.

At the end of a parallel-motion mode of one operation or a series ofsuch operations, the absolute relationship between encoder 104 and tiltactuator 60 is to be restored. This is executed by opening switchingmeans 108b and actuating reset element 108a to restore to zero the inputregister in unit 108 that stores input from comparator 90b. Thereafter,absolute position input data from program unit 104a has its originalsignificance in controlling the aim of Work head 18a, not altered byunit 108'.

The apparatus involving digital encoders 90 and 104 as Well as digitalencoders for other degrees of freedom in the apparatus describedrepresents a highly reliable form of program-controlled equipment, inwhich there is an absolute position for each numerical instruction foreach degree of freedom. The program as established is repeatablereliably on a point-to-point basis, free of errors such as might beintroduced in other forms of program control. In another form of programcontrol, the motion in any one degree of freedom from one point to thenext is established by counting the number of steps of advance. Each newposition is established as an increment in relation to the previousposition. In such a system there is a possibility of errors arising dueto spurious pulses and due to pulses being lost, a cumulative source oferror, and therefore the absolute-coordinate system as described in thepreferred type of control. However, it will be readily recognized thatthe parallel-motion controls 100 and 108 in FIGS. 3 and 4 and thecircuit of FIG. 4C can readily be used or adapted with the well-knownincremental pointto-point control systems, and with other forms ofprogramcontrolled motions.

The extent of motion in each degree of freedom when carried out underprogram control in each respective degree of freedom may be called aprogram-controlled motion. The parallel-motion mode of operation isbrought into effect under program control, as by energizing clutch 96(FIG. 3), or by closing switching means 108b for rendering added 108'operative. It represents a program-controlled mode of operation and itis another program-controlled motion. There is a tying-together of twodegrees of freedom wherein control of a primary degree of freedom causesmovement through a program-controlled arc while the linked degree offreedom moves through an incremental are from its initial position. Whenthe parallelmotion mode is in operation, the primary control such aselevation of arm 16 is linked to a related degree of freedom such astilt of head unit 18a. The latter is a dependent degree of freedomduring the parallel-motion mode. The secondary motions of work head 18aare equal and opposite to the primary motions of arm 16 in theparallel-motion mode of operation.

It will be appreciated that program control signals in FIG. 4C thatcontrol the operation of arm-tilting actuator 34 are also used,inversely, to control the work-head tilting actuator 50. Statedotherwise, there is no need for a separate program of signals fortilting the work head in the parallel-motion mode of operation, sincethe signals that control the arm elevation are used also to control theattitude of work head 18a. This kind of operation of the apparatus inFIG. 4C is applicable not only when the whole apparatus is beingoperated under program control, but also during the preparatory phase,when the program is being recorded, an operation more fully describedbelow in connection with FIG. 5. In that case, the values in encoders 90and 104 at the start of the parallel-motion mode of operation areentered in intermediate storage registers forming part of program units90a and 104a. Thereafter, during the time when actuator 34 is beingoperated by valve 34a under manual control to teach a motion sequence byrecording the manually controlled motions, the numerical changesproduced by encoder 90 are derived by comparator 90b and used (withreversed sign) to control the operation of valve a as already described.

This kind of operation is a distinct advantage, since the automaticparallel-motion mode of operation thus realized avoids the burden ofmanually controlling the attitude of work head 18a during theprogram-recording operations.

FIG. 5 is a simplified illustration of a form of program-controlequipment suitable for the apparatus of FIG. 1. This includes a rotarydrum 146 having a surface of readily magnetizable and magneticallyretentive material. This drum may be either a continuously rotating typeof storage drum, or it may be a form of magnetic drum that indexes fromone control position to the next.

13 The drum as shown is equipped with a first set of magnetic senslng orread heads 148 and another set of magnetizing or write heads 150, but itwill be understood that a single series of heads can readily be utilizedfor both sensing and recording. The control areas that are sensed at anyone moment by the series of heads 148 may be called a slot While theseries of areas sensed in successlon by any one of the heads 148 iscalled a track. Heads 148 are divided into as many groups as there are Idegrees of freedom, plus a few heads that are allocated to provided bydigital encoder 154, typical of the several encoders in the equipment ofFIG. 1 such as encoder 90 (FIG. 3) and encoder 104 (FIG. 4). Theditference between the coded numerical representation provided bysensing heads 148a and the position of actuated part of the apparatus,such as the elevation of arm'16 by actuator 34 as represented by encoder154, is derived by means of subtraction unit 156. The operation controlmeans 158 of the actuator in each degree of freedom is controlled byunit 156. Advantageously, unit 156 provides not only the on and offcontrol but also the direction of operation, corresponding to thealgebraic sign or sense of the difference between the values applied tosubtraction unit 156 by the temporary storage unit 152 and the digitalencoder 154. The details of this digital form of control are separatelywell known and may take a variety of different forms as, for example, inPat. No. 2,927,258 issued Mar. 1, 1960 to B. Lippel. Still further, theapparatus may be of a design to impart not only on and off control, anddirection or sense control, but also to provide rate control so as todecelerate the operation of the controlled actuator in the relateddegree of freedom as the end-point of the motion comes close. Themagnetic memory represented .vantage. In the illustrated apparatus, whenthe subtraction shows that there is correspondence between the tempo-.rary storage and the sensed coordinate for which the apparatus of FIG.1 has been programmed to operate, as one point in the series that makeup the program of motions, the next function or the next program stepbecomes effective. The controlled actuator may arrest the operated part,or motion of the actuated part may continue under control of the nextslot of the program drum.

There are as many groups of heads 148 as there are degrees of freedom,as previously mentioned, group 148a being assigned to one degree offreedom, group 148 being assigned to another degree of freedom, etc.Each additional group of heads 148b is associated with a duplicatesystem like that described for the group of heads 148a. Additionally,there is a group of heads 148c whose purpose is to provide controlfunctions for the apparatus. Thus, for example, at some part in theprogram it might be desired to institute a parallel-motion mode ofoperation. To do this, each synchro transmitter 90 is connected to itsreceiver 108, and each clutch 96 is activated, under control of arecording sensed by a head 148e, this control 96' optionally including atemporary storage register. Reset control 157 of the register 152 thattemporarily stores sensed digital codes can be rendered operative underthe same control 148c to prevent the value stored in temporary storageregister 152 from being changed in the sensing operations that follow.In the ensuing operation of the apparatus of FIG. 1 (when the next slotof the drum is in effect) the parallel-motion mode of operation wouldthen come into efl ect. At the end of such parallel-motion mode ofoperation, or at the end of a sequence of such operations, anothersensing head of the group 1480 may provide a signal to disconnect theservo transmitters and receivers, to deenergize clutches 96, and in thedevice of FIG. 4A, to close contacts 138, for restoring synchro receiver108 to its normal position. Concurrently this restores shaft 112 to theposition corresponding to that prevailing at the start of theparallel-motion operation. Where (as here) absolute coordinates arerepresented by the related digital encoder, the offset introduced by theparallel-motion mode of operation is eliminated, and absolute-valuerelationship between encoder 104 and shaft 112 is restored. Thefollowing operations in the program are controlled by the sensing heads148a, 148b, etc.

Restoration of the synchro receiver 108 (or its equivalent) to thestarting position at the end of a parallelmotion step or series of stepsin a program may well be desired even Where the encoder 104 is omittedin favor of a variety of other forms of program-responsive drivecontrols that may not involve an encoder of absolute positions. A devicefor controlling or monitoring a programcontrolled motion as anincremental displacement or as a discrete series of steps from theprevious program-controlled position is an example of another form ofcontrol with which the parallel-motion mode of operation is useful, andstill others are known.

The program on drum 146 is recorded as is discussed in greater detail inthe above-identified Devol patents. Briefly, however, a new program canquickly be taught to the memory drum by manually controlling theapparatus of FIG. 1 to execute the desired program and, at each step ofthe sequence of motions that is desired, causing the coordinates of thatposition to be recorded. For this purpose, digital encoder 154 may beconnected by switch to the control circuit 162 of the related group ofrecording heads 150a. These heads (when energized) record the codecombination represented in encoder 154, as to each step in the program,for each of the different degrees of freedom. Additionally, it isunderstood that appropriate manually controlled means are to be providedfor causing recording heads 150s to record the necessary functioncontrol portions of the recorded program. During program-controlledoperation of the apparatus, the drum-advancing means 161 operates undercontrol of subtraction means 156 and a function-control sensing head148e, via switch 163. This switch is shifted to manual control duringthe teach activities.

The apparatus of FIGS. 15 inclusive represents a highly flexible type ofequipment that is readily adapted to perform a variety of functions, asalready mentioned. The foregoing parallel-motion mode of operation isespecially important in the apparatus shown in FIGS. 6 and 12 and theirrelated figures.

FIG. 6 illustrates, somewhat diagrammatically, apparatus that is broadlysimilar to that of FIG. 1, in that unit 10a also has a base 12, avertical post 14 that is rotatable about its vertical axis, an arm 16that is pivoted to move through various angles of elevation about apivot 16a at the top of post 14, and head 18 having a work head 18aincluding article-gripping jaws 48. The head and the jaws in FIG. 6 arecapable of both tilting and swinging motions and have control meansidentical to that in FIGS. 1-5 (omitted from the drawing in FIG. 6)adapting the head to both program-controlled operation and operation inwhat has been called the parallel-motion mode. In FIG. 6, the actuator34 for controlling the angle of elevation of arm 16 has a hydraulicservo control valve 166 that is capable of operating arm 16 up and down,decelerating the motion of the arm as each desired position isapproached.

The hydraulic actuator in arm 16, such as actuator 38 in FIG. 2, iscontrolled by a hydraulic valve 168 in FIG. 6. A control arm 170 isoperable about a pivot 172. The control end of valve 166 and its bodyare connected to arms 16 and 170 so as to remain parallel to post 14.Valve 166 and actuator 34 act as a hydraulic servo system so thatoperation of control arm 170 is reproduced post 14 causes master control192 to control the servo slave motor base 12 to rotate post 14correspondingly. Preferably a master valve is used as control 192 with a,slave hydraulic .motor in base 12. Accordingly, motions of arm 170about the axis of post 14 are reproduced by the post and by arm 16 sothat arms 16 and 170 remain in a common plane that passes through theaxis of the post.

A rod 175 is slidably mounted within arm 170. One end of a cable 178 issecured to the rod 38a which moves head 18 radially, in the sense of asystemof motions in polar coordinates. Cable 178 extends about a pulley180 coaxial with the, pivot of arm 16. The other end of cable 178 iswound abouta drum 182 that is secured to post 14, and has a bearing axisparallel to that of pulley 180. A second cable.1-86 has one end woundabout drum 184,

the latter being half the diameter of drum 182 and v se cured thereto.Cable 186 extends about a pulley-188' coaxial with pivot 172, and theoppositeendof thiscable is secured to the control portion of valve 168,the body of which is secured to rod 175. Pulley 188 is helf the diameterof pulley 180. Suitable means represented by spring 190 acts on thepart-of valve 168 to which cable 186 is attached, for maintaining thecable under tension. For example, this spring represents a pneumaticcylinder in arm 170 whose piston is connected to rod 175 and constantlybiases rod 176 toward the right in FIG. 6. Valve 168 and the radialactuator of arm 16 (see actuator 38, FIG. 2) form a hydraulic servodrive. When the valve control shaft 176 is shifted out of its normalposition in relation to the body portion of the valve, then the actuatorin arm 16 causes rod 38a to operate cables 178 and 186 as a feedbackservo connection in the direction to restore the normal conditionbetween the valve body and the control part of valve 168. Move ments ofrod 176 along its length are accordingly reproduced as proportionalmovements of head 18 along arm 16.

Rod 176 represents what may be called a master lever 'for controllingthe three valves 166, 168 and 192 that 'control the primary motions ofelevation, azimuth and will be reviewed below.

The mechanically operated valve 166 for servo "actuator 34, and themechanically coupled master 168 with its slave actuator 38, and themechanically actuated valve 192 and its slave motor 12 are direct andeffective, but. by no means unique. Thus, if the mechanical couplingbetween each master and slave as shown were considered objectionable,master and slave potentiometers in a bridge can be used to control thedirection and operation of each of these actuator controls 166, 168 and192, and a variety of other servos can be used between each of outputpoints 166, 168 and 192 of the control converter 170, 196 and therespective controls for the actuators that operate apparatus 12, 14 and18.

The details of apparatus 196 are shown in FIGS. 7, 8 r

and 9. Unite 196 comprises a-pair of rails 200 ,which slidably supportbearing members 202 and' 2022; of a bridge bar 204. The oppositelyextending endsfof hydraulic actuator 206 operate a chain 208 thatextends about sprockets 210 and 212. These sprockets are secllffid l0l1,af1 .214 and 216 which carry pairs of sprockets .bydigital encoder232..

slidable in block 242.

" and 220 that are twice the diameter of sprockets 210 At th l ft inFIGS; 7 and s, shaft'230ex ndinaparallel .to rails 200 is longitudinallygrooved or pined and has suitable end bearings for rotatably supportingthe shaft. Shaft 230 is coupled towshaft-position encoder 232 and todrive motor 234 by suitable gearing. Sprocket 236 has lateral bearingsin bridge bar 204 and lidable along shaft 230. Sprocket 236 isinternallylkeyed. o. as

.to be rotated by shaft 230. A chain 238 driven -by sprocket 236 andextending about sprocket 240 hasits. extremities fixed to a block 242that has slide bearings for operation along bar 204. Accordingly,operation of motor 234 is efiectiveto shift block 242 horizontally alongbar 204, and the position of bar 242 along bar 204. isf. rii onit r.ed

At the rightin FIGS. 7 .and 8,. afurthepshaftlZj U tending parallel torails 200 is longitudinally grooyed or splined and has rotary;.endbearings. Shafti'244, is rotated by motor246 and theangular position ofshaft 244 is monitored by an analog-to-digital converter onencoder 248.An additional splined shaft 250 parallel to bridge bar 204 has its endssuitably supported in bearings on bridge bar 204. Shafts 244 and 250ar'ef coupled by bevel gearing 252. A pinion 254 having lateral'bearings in block 242 is slidable along shaft 250 and is'internallykeyed so as to be rotated by splined shaft 250. Pinion 254 meshes with avertical rack 256. that is accurately It will be understood that in allof the foregoing drive couplings in FIGS. 7 and 8, due precautions willbe observed for avoiding looseness or backlash at thegearing and forassuring accurately controlled sliding motionfree of looseness wherethis is needed. p

At the top of rack 256 there is a rotatably mounted collar 258, and theforked end of master lever 176 (see FIG. 6) has snug-fitting bearings incollar 158. Motors 206, 234 and 246 move rack 256 along X, Y and Zcoordinates, and correspondingly move the operating end of'master lever176 of the apparatus in FIG. 6. The "position of rack 256 in each ofthese coordinates is'lnonit'ored by respective digital encoders 224, 232and 248.

The master lever 170 and its associatedcable 186 and its pulley 188 andits wind-up drum 186 are all accurately made to half-scale that of arm1638a, pulley 18'0and wind up drum 82. To complete the symmetry betweenarm 1'638a and master lever 170-176,- thedistance between pivots 16a andthe axisof these drums is'twicethe distance between pivot 172 and theaxis of these drums. 'Accordingly the'motio'n's of control head2'58correspond to those of arm 16 in angles of elevation and azimuth,and theradial extent of work head 18 remains twice that of control head258. I p

It has been indicated that the apparatus o f'FIG. "6 is very similar,basically, to that of FIG. 1. It should therefore be'understood thatth'e'servo transmitters and receiv- "and azimuth, Despite therectangular controls use'din FIG.

' 6'for the primary motions of the arm,"the'parallel'-motion mode ofoperating work head 18'is ffully effective.

The apparatus of FIGS. 7 and is program-controlled byfapparatus of thetype shown in FIG. j iandidescribed above. However, whilepolancoordinates are used in the programfor the apparatus of FIG. 1,the. elevation, the azimuth, and the radial extension of. head unit 18a,are

- 17 expressed in the program for the apparatus of FIG. 6 in terms ofrectangular coordinates, i.e., digits that define the coordinates ofcontrol head 258 at the top of rack 256 and at the end of the masterlever 176. The polar-coordinate operating unit 12, 14, 16, etc., of FIG.6 is controlled by master servo lever 176, and thisis operated by arectangular-coordinate manipulator 196 (FIGS. 7 and 8) that isprogram-controlled.

A program can be taught to the program storage drum in the followingmanner. Head 18 can be shifted to various desired positions bycontrolling motors 206, 234 and 246 manually. Arm 16 responds in itsbasic motions of azimuth, elevation and length. When each desiredposition of head unit 18 is thus established, the rectangularcoordinates as represented by digital encoders 224, 232 and 248 arerecorded. These three coordinates may represent only part of therecording that is effective with reference to each location of head unit18, for at each such location the other program entries may also beneeded, representing related operations such as jaw-opening or closingcontrols, and one such recording is the start and end of theparallel-motion mode controls. If the apparatus is then changed to itsautomatic program-controlled mode of operation, the motions executed byhead unit 18 and jaws 48 will then accurately repeat the taught motionsunder control of the drum recording. The recorded program relates to anarticle A (FIG. 6) that is assumed to be at rest.

In FIG. 6, work head 18a is shown as being cooperable with an article Aon a conveyor 260 which is operated by a drive motor 262 and sprockets264 on shaft 266. A servo transmitter 268 monitors the advance ofconveyor 260. During all of the recording of a program to enable headunit 1821 to execute a series of operations on article A, conveyor 260will be at rest.

The conveyor can then be started, and an article can be mounted on theconveyor at an accurately known location. At the same'time, the signalgenerated by synchro transmitter 268 will be coupled to synchro receiver226. Accordingly, the position of bridge bar 204 along its rails will bemodified progressively so as to introduce a departure between the actualposition of control head 258 and, correspondingly, the actual positionsof those parts in the at rest" program that is recorded on the drum. Inan example, article A in FIG. 6 may represent a pallet (FIG. 10) and thejaws 48 of the apparatus in FIG. 6 may be automatically operated so asto seize, transport and discharge a succession of articles carried bythe conveyor. In another example, the jaws 48 are formed as weldingjaws, programmed for making a series of Welds at different spots on anarticle carried by the conveyor; or a glue-spotting tool can replacejaws 48, and so forth. The program that was taught to the apparatuswhile the conveyor was at rest is modified by the off-set factorintroduced by servo system 226, 268 to represent the speed of theconveyor. Of course, servo motor 226 drives bridge bar 204 along rails200 at half the speed of the conveyor by properly proportioning thegearing that drives bridge bar 204. The program is thus executedsuccessfully and accurately despite the motion of the conveyor thattakes place while the program is being executed automatically, anddespite the fact that the program was recorded with the article A atrest.

There may be no requirement for the secondary" degrees of freedomrepresented by tilt and swing of Work head 18a (FIGS. 1 and 2) to besubject to independent control in the apparatus of FIG. 6. Instead workhead 18a may be constrained to a fixed attitude in space using theparallel-motion mode of operation and control means of FIGS. l5. In thatevent, the tilt and swing control recordings would remains unchanged forall motions of arm 16. These two recordings should establish ahorizontal attitude of the axis of work head 18a. The axis of the workhead as shown passes midway between jaws 48 and passes perpendicularlythrough shafts 18c and 18d which should be parallel to pivot 16a andpost 14 of arm 16 in this 18 operation. Work head 18a would then movethrough tilt and swing angles that are equal and opposite to theelevation and azimuth angles of arm 16.

As shown in FIG. 6A, work head 18a at the start of a motion (solidlines) moves through an angle A in reaching the final position 18a thatequals the change in elevation B of arm 16. FIG. 6A demonstrates alatitude of flexibility of the apparatus. By mounting, adjusting oroperating jaws 48 movably relative to 18a so that the jaws aim down (orotherwise) while shaft 18d is parallel to post 14, the attitude of thehead can be maintained consent throughout a sequence of motions in theparallel-motion mode. Thus, the apparatus is not inherently limited tothe aforementioned horizontal attitude in operating work head 18a.

The parallel-motion servos are maintained constantly in operation forthis type of operation, not only during the program-controlled operationbut also during the teach" procedure of recording a control program forthe apparatus. If desired, just before each program cycle of operationsin the parallel-motion mode starts, the attitude of work head 1821 maybe normalized to eliminate errors that could arise, i.e., in case themaster and slave servos and 108 (FIGS. 3 and 4) were to fall out ofstep. One of the heads c may be used to record a control for'such anoperation on the program of drum 146. In this normalizing operation, arm16 is ideally perpendicular to conveyor 260 and the axis of work head18a is aligned with arm 16 and both are horizontal.

Synchro transmitter 268 and synchro receiver 226 are to be initiated inoperation under program control from a starting condition at the startof the program, and they are to be restored to their starting conditionat the end of the program. This is accomplished in precisely the manneras that described above in connection with FIGS. 1-5, and particularlywith respect to FIG. 4. It follows that the apparatus in FIG. 6 willoperate under control of a set of rectangular coordinates in themagnetic memory represented by drum 146 despite the essentially polarcharacter of the apparatus 12, 14, 16 and 38. The motion of the conveyordoes not introduce any changes in the recorded rectangular coordinatesof the program, and yet the execution of the program by the polarapparatus takes into account all of the complex and progressive changesof azimuth, elevation and lengthwise changes of arm 16 that arenecessary for jaws 48 to reach predetermined parts of an article and tokeep the jaws moving in step with particular parts of an article whencarried in the straightline path of the conveyor.

The coordination of the conveyor in FIG. 6 with the rest of theapparatus in that figure represents a distinctive feature of theinvention, but this apparatus has still other advantages, apart from theconveyor. Thus, it may be desired to develop a series of pallet-loadingor pallet-unloading techniques where there are many rows of articles ona pallet, many columns of articles, and many layers of articles on thatpallet (FIG. 10). It would be relatively tedious to carry out themanually controlled motions of the apparatus for teaching such aprogram. The apparatus of FIG. 6 with its rectangular manipulator (FIGS.7 and 8) has the distinct advantage of being able to operate during ateach mode by using the X, Y" and Z encoders 224, 232 and 248, togetherwith a means for executing a sequence of steps defined by successiveincrements introduced into a rudimentary computer. The dimensions ofeach carton are known, and hence center-to-center distribution of thecartons along the X axis, along the Y axis,

and along the Z axis is also known. The X, Y and Z.

coordinates of the first carton location are readily determined bymanually operating the apparatus to deposit a carton at that location.This set of coordinates can be fed into a computer, together with thethree center-to-center X, Y and Z distances desired for the cartonspacing within a row, for the row-to-row spacing, and for the layer-tolayer spacing, plus the number of cartons in each row, the number ofrows, and the number of layers. After the first carton has been spottedphysically by operating the apparatus, and the coordinates of thatlocation are entered in the program drum 146, then the computer cansupply the X, Y and Z digital coordinates to be entered into successiveslots of the program drum. Each new program becomes a simple matter.Indeed, a computer can be used to record a series of programs on tapefor each difierent grouping of articles to be palletized, and each suchprogram can be transferred into drum 146 when needed or such tapes caneven be used in lieu of such a program on drum 146 for controlling theautomatic operation of the apparatus of FIGS. 6-9. Other modes ofcontrol of the elevation, azimuth and radial positions of apparatus 10by means of the X-Y-Z control apparatus 196 can be devised for suchpatterned-location operations such as palletizing, where X, Y and Zinformation of the patterned locations is available.

It may at times be important for the program-controlled apparatus toexecute a program involving a number of operations on an article on amoving conveyor, and to cooperate with one or more stationary locations.Thus, for example, it may be desirable for articles at one supply pointor a series of articles located at spaced-apart supply points adjacentto a conveyor to be picked up in a prescribed sequence and transferredto an article being transported on a moving conveyor, as for assemblingparts to a machine being assembled while the machine base is advancingon the conveyor or for loading a pallet on the conveyor. Similarly, itmay be desired to remove a series of articles from a pattern oflocations within a modular area of a moving conveyor, and to transportthose articles and deposit them in succession at a delivery point or ina prescribed pattern of delivery locations. Such a program can berecorded with the conveyor at rest. Under manual control, the apparatus10a is caused to execute operations in any required sequence withrespect to the article or modular area to be advanced by the conveyor,and with respect to one or more fixed locations adjacent to theconveyor. Then the automatic operation can be accomplished by having thecontrol apparatus equipped with a means for introducing an off-set inthe programcontrolled motions that are executed in relation to a movingconveyor and, for each motion that is to be executed in relation to astationary location, to restore the program-control means to the moreusual form of control in which there is no such off-set. This characterof operation can be achieved by incorporating the structure of FIG. 11in that of FIG. 7, as a modification of a part of FIG. 7.

The apparatus of FIG. 11 includes digital encoder 224, synchro receiver226, and differential gearing unit 228 that introduces an off-setprovided by synchro receiver 226 between the value of encoder 224 andthe position of shaft 216. A mechanism 261 is interposed between synchroreceiver 226 and differential gearing 228. The purpose of mechanism 261is to enable synchro receiver 226 to introduce a progressive off-set inproportion to the extent of motion of the conveyor from a starting timeof a complete program of motions including conveyor-related motions, andto restore the program free of off-set during the execution ofoperations not concerned with conveyor motion. In this way the apparatuscan perform motions related to stationary articles and devices atstationary locations adjacent to the conveyor, and to catch up with aprogressively advancing discrete area of the moving conveyor. The entiretravel of the conveyor from start of the program is taken into account,without special concern for the time taken by the apparatus in executingprogram-controlled motions related to stationary locations.

Mechanism 261 includes gear 263 that is supported on a shaft 265 andmeshes with the pinion 267 that provides offset input to differentialgearing unit 228. A block 269 extends laterally from gear 263 and is indriving engagement with a pin 271 that extends laterally from anothergear 273. This driving engagement is true for only one direction ofrotation of gear 263. A torsion spring unit 275 has one end of theinternal spring connected to shaft 265, and the other end of theinternal spring connected to tubular shaft 277 that is rotatablysupported on shaft 265. Gear 273 is fixed to shaft 277. Torsion springunit 275 biases gears 263 and 273 in the required directions to maintaindriving connection between block 269 and pin 271. Pinion 279 that mesheswith gear 273 is rotated by synchro receiver 226 in the direction todrive pin 271 away from block 269. As synchro receiver 226 operates gear279, gear 273 rotates and, due to torsion spring unit 275, gear 263'rotates likewise. This introduces the previously described off-set intothe rectangular manipulator 196 of FIGS. 6, 7 and 8 to compensate thepre-recorded program for the motion of the conveyor.

Gear 263 has a pin 281 that is in engagement with a stop 283 at thestart of the program. A torque motor 285 is connected to gear 263 andshaft 265 and is effective when energized to drive gear 263 so that itspin 281 bears against stop 283.

At the start of the program, synchro receiver 226 is not energized.Torque motor 285 is energized under control of the program on drum 126(FIG. 5) to press pin 281 against stop 283, and then motor 285 isdeenergized. Under program control, synchro receiver 226 is energizedand starts to rotate coordinately with the travel of the conveyor. Thecoupling mechanism 261 is then effective to transmit the off-setprovided by synchro receiver 226 to the differential gearing unit 228.Consequently, the motions of apparatus unit 12, 14, 16, etc., willexecute the originally recorded program, modified to introduce theoff-set for compensating the program for conveyor travel. Synchroreceiver 226 continues to rotate and to rotate gear 273' during theexecution of the entire program. However, if at some time in the courseof the program, the apparatus unit 12, 14, 16, etc., is to execute anoriginally recorded program motion in relation to a fixed locationalongside the conveyor, then torque motor 285 is energized under programcontrol to restore gear 263 to its starting position. This restores thedirect relationship between encoder 224 and shaft 216 that existedduring recording of the program, free of any off-set. When it is nextdesired to execute another operation in relation to the conveyor, torquemotor 285 is deenergized, and the torsion provided by spring unit 275 isthen effective to restore the off-set corresponding to the actualconveyor advance from the start of the program. Spring unit 275 advancesgear 263 to the extent limited to engagement of its block 269 with pin271 on gear 273 that has been continuously driven by synchro receiver226. In this way, an entire program can be pre-recorded to includeoperations of the transfer unit which relate to stationary locations,and other operations that relate to a discrete moving section of aconveyor; and later the program can be executed automatically, with theconveyor operations alternating with the stationary operations executedby the transfer apparatus. When the mechanism of FIG. 11 is utilized,the apparatus in FIG. 5 is to include a recording head 1500 and asensing head 148c with a related circuit for controlling torque motor285.

A further embodiment of various aspects of the invention is illustratedin FIGS. 12, 12A, and 1316. The article-handling unit 10b of FIG. 12includes a base 12', a post 14' that is rotatable about a vertical axis,an arm 16' that moves about a horizontal pivot 16a, and a head 18 on theend of a shaft 38a that moves head 18 to various radial lengths,measured from pivot 16a. Work head 18a carries a pair of jaws 48. Head18 has the same actuating means as in FIG. 1 so that the jaws can bemoved through various tilting motions about a horizontal axis (parallelto pivot 16a) and various swinging motions about an axis perpendicularto the tilting axis. The same encoders and off-set servo receivers areprovided in the apparatus of FIG. 12 for the swinging motion of workhead 18a and for the tilting motion of work head 18a as in FIG. 1.

Transfer apparatus 10b is capable of being taught a program of motionswith respect to a stationary space, e.g., the space containing anarticle A while at rest, and then the transfer apparatus 10b is capableof executing that program on article A when the article is carried on amoving conveyor 260 as in FIG. 6. In common with the apparatus in FIG.1, apparatus 10b includes an azimuth angle encoder 290 which monitorsthe rotation of post 14' about its vertical axis, and it includes anencoder 292 that monitors the angle of elevation of arm 16, and itfurther includes a radial-position or arm-length encoder 294 thatmonitors the distance between pivot 16a and head 18. Motor 20 rotatespost 14 about its vertical axis, actuator 34 operates arm 16' aboutpivot 16a, and a hydraulic actuator in arm 16' (as in FIG. 1) operatesshaft 38a outward and inward, all subject to the same program controlwhen article A is at rest as the apparatus of FIG. 1.

Apparatus 10b in FIG. 12 has an off-set servo receiver 296 that iscoupled through a differential gearing unit 298 to encoder 290 and topost 14' via pinion 80b and gear 80a. Similarly, an off-set servoreceiver 300 is coupled via differential gearing unit 302 to encoder 292and to gear sector 304 that is rigidly connected to arm 16'. Finally,encoder 294 that monitors the length of arm 16', 38a is coupled to anoff-set servo receiver 306 and to drum 84c (as in FIG. 1) viadifferential gearing unit 308. Off-set servo receivers 296, 300 and 306are included for introducing a compensating factor that adjusts theoperation of apparatus 10b for the motion of the article A on aconveyor, after the apparatus has been taught a program with respect toa stationary article A. These compensations will be appreciated from aconsideration of FIG. 12A.

It is understood that a program has been recorded in the memory of theapparatus (FIG. While an article was at rest on conveyor 260 (FIGS. 12and 12A). This program involves a motion of the head 18 to position18-1. Then there is a dwell, the article and the head remaining at restfor a time interval during the teaching of the program. The dwell mayallow for a Welding operation or for a drilling operation by a drillthat moves outward relative to head 18, or a spot-coating operation, orthe like. Subsequently, head 18 is moved to a second programcontrolledposition 18-2 and there another dwell is required in this illustrativepro-gram. Any further steps follow, as needed.

After the whole program has been recorded with article A at rest, theprogram is executed with the article on conveyor 260 which is then setin motion. The apparatus b moves head 18 to position 18.-1 at the startof the program, with arm 16 in position 16-1. During the first dwell ofthe program, arm 16 moves through an angle to position 16-1a, to keephead 18 in constant position in relation to the moving article.Thereafter, instead of arm 16 carrying head 18 to position 18-2, no suchmotion is undertaken. This is because the at-rest position 18-2 of head18 has now been changed by motion of the conveyor during the dwell.Programmed position 18-2 has now become position 18-2a. Accordingly, arm16 should move to position 16-2a. During the second dwell, to remain incooperation with the same p-art of the article represented by originalcoordinate 18-2, arm 16 must move from position 16-2a to position 16-2b.Prominent compensations are needed between the record-controlledpositions and the program carried out in relation to the moving article.

The height of head 18 above the horizontal x, y plane (through the pivot16a of arm 16) remains constant during the first dwell, while head 18moves from position 18-1 to position 18-1a. This is a straight-linemotion, parallel to the path of conveyor 260. Initially, as arm 16-1swings toward vertical plane x, 2, arm 16', 38a becomes shorter so as toinvolve an arm-length correction C-1. Thereafter, as head 18 moves fromthe x-z plane to position 18-1a, the arm length will increase to theextent of compensation 0-2. (In the chosen operation, arni 16 has movedthrough a greater angle beyond plane x, z in reaching position 16-1athan it traversed from position 16-1 to plane x, 2.) C-1 represents adecrease in arm length and C-2 represents an increase in arm length, ascompared with the recorded arm length.

During the swing of arm 16' from the position 16-1 to the vertical planex, 2, there is an increase in the angleof-elevation of arm 16. This isbecause the radial extent of head 18 has changed, from position 18-1 toa shorter radial position and it has maintained a constant distance fromthe x, y plane (i.e., conveyor 260). The angle of elevation of arm 16'decreases as arm 16 moves beyond plane x, z to position 16-1a. Thechanges in angle of elevation to keep head 18 at the position 18-1required by the recorded program involve further compensations.

From position 18-1a, head 18 must not move to the originally programmedposition 18-2 but, instead, head 18 must move directly to position 18-2ato take into account the travel of the conveyor during the first dwell.Position 18-2 in this example is originally at the far side of plane x,z. By the time head 18 has moved to the position 18-2a (located along astraight line parallel to conveyor 260, from position 18-2) it hasbecome necessary for the length of the arm to increase by a compensationdistance C-3. The angle of elevation of head 18 has decreased a little(compared to the angle of elevation at position 18-2 of the at-restprogram) and of course there has been a sweep of arm 16 through asubstantial azimuth angle to reach position 16-2a. Thereafter, when head18 moves from position 18-2a to position 18-2b, there is furtherelongation of the arm requiring an armlength compensation C-4, comparedto the original programmed arm length. There has also been a change inazimuth angle, and there has been a reduction in angle of elevation.

Mechanism 310 which is best illustrated in FIGS. 12 to 16, inclusive,provides all these compensations. This mechanism includes an arm 312that is pivoted about axis 312 on a bracket 314 carried on a collar 316that is coaxial with shaft 14 but rotatable on shaft 14' about thevertical axis. A companion arm 312a is similarly carried by a suitablebracket on collar 316a that is rotatable about a stationary shaft 14aparallel to post 14 but spaced laterally from that post. An armextension 318 is telescopically received in arm 312 and, similarly, anarm extension 318a is telescopically received in arm 312a. A sphericalbearing 320 fixed to shaft 322 is captive in a suitable socket in theend of arm 318. A spherical bearing 320a also fixed to shaft 322 issupported by arm extension 318a. Arms 312 and 312a are parallel to eachother at all times. Balls 320 and 320a rotate in their sockets. A shaft323 is supported by brackets 325 and 327 depending from arms 312 and312a, spaced substantially below arm 324. Pinions 329 in these bracketsmesh with rack teeth along arm extensions 318 and 318a. Shaft 323connects pinions 329 so that both pinions rotate in unison, maintainingarm extensions 318 and 318a equal in length. Shaft 323 has a flexible ora universal rotary drive connection to each pinion 329 that accommodatesangular shift of arms 312 and 312a in relation to the shaft.

A third arm 324 is carried on pivot 324' extending perpendicularlythrough post 14'. Arm extension 326 is received telescopically Withinarm 324. An externally spherical unit 328 on threaded shaft 322 iscarried in a socket in extension 326, and is keyed against rotation inextension 326. In operation, parts 320, 320a and 328 pivot about axesperpendicular to shaft 322 and to their supporting arm extensions. Aservo receiver torque motor 330 is carried by shaft 322 and is arrangedto operate shaft 322 in the direction to drive nut 328 away from thecompanion part 320. An arcuate part 330a extends from arm extension 318to constrain the motor frame from rotating. As will be seen, theposition of arm 312 and its extension 318 represents the originalprogrammed 23 azimuth, elevation and length of the arm, whereas theangular position of arm 324 and its extension 326 represents the actualor compensated azimuth, elevation and length of arm 16, 38a.

A fourth arm 332 is supported on the horizontal pivot of arm 324. Anannular plate 334 is carried by a slide bearing 335 on post 14. Raisedbrackets 336 and 337 of arms 312 and 332, respectively, engage plate334. This plate is biased against bracket 336, by gravity for example,while arm 332 is suitably biased upward so that its bracket 337 bearsagainst plate 334. Plate 334 is thus effective to maintain arm 332 atthe same angle as that assumed by arm 312. Plate 334 is spaced from arm324 to provide clearance for arm 324 to assume larger angles ofelevation than arm 312. Arm 332 carries a servo torque transmitter 338whose rotor carries a pinion 348 meshing with a gear sector 342 carriedby a bracket 344 upstanding from arm 324. The angle through which gearsector 342 operates servo transmitter 338 is a measure of the change ofelevation of arm 324 relative to the programmed elevation represented bythe elevation of arm 312. This change provides a compensation signalduring conveyor operation, and is discussed more fully below.

An arm 345 extends rigidly from post 14 and supports a servo transmitter346. A further arm 348 extends from bracket 316. One end of a rack orgear sector 350 is secured to bracket 348. A pinion 352 on the shaft ofthe servo transmitter 346 meshes with gear sector 350. When angularitydevelops between arms 312 and 324, as represented by their axes 312' and324 (FIG. 15) this angularity is measured by the rotation of servotransmitter 346. The signal of servo transmitter 346 represents theazimuth compensation between the programmed position of arm 16 and itscompensated position during conveyor operation.

Motor 330 is a servo torque receiver that drives nut 328 along shaft 322in synchronism with the conveyor travel.

Arms 312 and 324 carry servo transmitters 354 and 356, respectively,e.g., synchro torque transmitters. These servo transmitters have pinions329 and 357 which mesh with rack teeth along extensions 318 and 326,respectively.

Referring once again to FIG. 12, a cable 360 is shown having one endsecured to shaft 38a that moves with head 18. Cable 360 passes around apulley 362 coaxial with shaft 16a, and then around a drum 364 that ismounted on post 14'. Wind-up drum 364 has an internal tensioner such asa torque motor to maintain cable 360 under tension. Another cable 366 iswound about a drum 368 coaxial with drum 364 and fixed thereto. Cable366 extends about a pulley 370 that is rotatably mounted on post 14',and the remote end of cable 366 is secured to a bracket portion 372 ofextension 326 (FIG. 15). An internal compression coil spring orfluid-pressure cylinder in arm 324 presses extension 326 outward andmaintains cable 366 tensioned.

A rod 374 (FIGS. 12 and 15) extends between arm 16 and arm 324 formaintaining these arms parallel, as to their angle of elevation. Rod 374is parallel to post 14'.

The operation of the apparatus thus far described may be considered atthis point. Servo torque receiver motor 330 on shaft 322 receives asignal from the servo torque transmitter 368 coupled to the conveyor360, so that motor 330 rotates at a rate that represents the speed of aconveyor. Rotation of motor 330 drives arm 326 away from arm 318. Theproportions of compensator 310 including its arm lengths, pulley 370,and drum 368 are all scaled down, for example, to one-half of arm 16,38a, pulley 362 and drum 364; and the distance between pulley 370 anddrum 368 is accordingly half that between pulley 362 and drum 364. Servotorque receiver motor 330 advances the end of extension 326 alongthreaded shaft 322 accordingly at one-half the linear speed of advanceof the conveyor. The length of shaft 322 between extensions 318 and 318ais made sutficient for the apparatus to execute the programmed sequenceof operations during the travel of an article on the conveyor pastapparatus 10b.

The apparatus that includes motor 20 and digital encoder 290 that arecoupled to the vertical post 14' tends to operate that vertical post asif the article A with which head 18 is to cooperate were not moving.However, operation of the conveyor rotates servo torque transmitter 268and operates torque receiver motor 330 correspondingly, and as a result,an angle develops between arms 312 and 324 (FIG. 15). An equal angledevelops between arms 345 and 348 (FIG. 14), with the result that servotorque transmitter 346 produces an output that is a measure of thisangle. Torque transmitter 346 is coupled to servo torque receiver 296(FIG. 12). The servo system 346, 296, acts through differential gearing298 to introduce an off-set between the actual azimuth angle of post 14'and that which is represented by encoder 290, to an extent thataccommodates the travel (at any given instant) of article A on conveyor260 from the start of the recorded program. A suitable index element onthe conveyor, or on article A, may be used to trigger the start of theprogrammed operation of apparatus 10b, as in Pat. No. 3,283,918.

Arms 324 and 16. are both pivoted to shaft 14, and they both swingthrough equal azimuth angles concurrently. The actual position of arm 16at any given point in the program is actually the recorded azimuthangle, subject to the off-set introduced by servo system 346, 296.Accordingly, arm 312 lags arm 324 by this off-set angle; and the angularposition of arm 312 is, consequently, the position that arm 16 wouldhave assumed if there had been no off-set azimuth angle.

The radial length oflarm 16, 38a tends to operate under program controlin accordance with encoder 294. However, an off-set length is introducedby servo torque receiver 306, for adjusting the radial position of head18 in accordance with the recorded program and in accordance with thecompensation or correction required to take into account the motion ofthe conveyor. The signal for synchro torque receiver 306 is supplied inthe following manner. The radially outward bias of the internal springor air cylinder within arm 324 acting on extension 326 presses shaft 322transversely, tending to move shaft 322 away from post 14'. Arms 312 and312a are also preferably equipped wth internal biasing means for urgingextension 318 and 318a outward, tending to move transverse threadedshaft 322 bodily away from posts 14' and 14a. This outward biasmaintains cable 366 under tension. Accordingly, the radial extent ofhead 18 from pivot 16a of arm 16', 38a remains proportional to thelength of arm 324, 326. Servo torque transmitters 354 and 356 (FIG. 14)on arms 312 and 324 operate synchro torque receivers 375 and 376 (FIG.16). These synchro receivers are connected to a differential gear unit378 arranged to operate a synchro torque transmitter 380 in accordancewith the difference between the rotations of each synchro torquetransmitter 354 and 356. The output of synchro torque transmitter 380(geareddown to the one-half scale of unit 310 compared to arm 16', 38a)operates synchro torque receiver 306 (FIG. 12) Differentials 378 and 308may be direct-connected it convenient, omitting servo units 306 and 380.

So long as arm 324 and its extension 325 are face-toface with arm 312and its extension 318, then there is no difference in the rotationbetween servo torque transmitter 354 and 356, irrespective of the lengthof extension 326 as determined by cables 366 and 360. However, whenservo torque receiver motor 330 operates to shift extension 326 awayfrom extension 318 (FIG. 15) then a difference develops between thelength of arm 312, 318 and arm 324, 326. This difference is derived bythe servo elements in FIG. 16 and introduced by servo receiver 306 as anoff-set or departure between the actual length of arm 16', 38a and thelength of that arm called for by the program. This difference resultsfrom the effect of servo torque receiver 330 and represents thenecessary compensation inlength of arm 16', 38a, to accommodate therecorded vprogram to the travel of the conveyor.

The angle of elevation of arm 16' is that produced by actuator 34 undercontrol of the stored program and elevation-angle encoder 292. It willbe recalled that link 374 constrains arm 324 to remain parallel to arm-16. When servo torque receiver motor 330 operates shaft 322 and causesarm 324 to swing away from arm 312, the angle of elevation of arm 324changes in relation to that of arm 312. Arm 312 remains at a positioncorresponding to the actually recorded program. The net etfect of theangular movement of arm 324 relatively away from arm 312 results in arm332 moving through an angle in relation to arm 324. This motion operatesservo torque transmitter 338 to transmit an elevation compensatingsignal to servo torque receiver 300, thereby to adjust the angle ofelevation of arm 16', 38a as it moves through the variousprogram-controlled motions for coordination with the conveyor asillustrated in FIG. 12A.

In FIGS. 12-15, each of the primary program-controlled motions involvesa mechanical feedback connection between the transfer apparatus b andits compensation signal generator mechanism 310. Arm 324 is carried on apivot transverse to post 14 and parallel to pivot 16a. Bracket 345 isfixed to post 14 and carries a servo torque transmitter 346 that isrotated by gear sector 350 on a bracket 348, for providing the azimuthangular compensating transmission. Bracket 345 thus represents a directfeedback connection to mechanism 310 from the controlled part ofapparatus 10b. Cables 360 and 366 form a mechanical feedback connectionbetween arm 16, 38a of the apparatus 10b and arm 324, 326 of thecompensation mechanism 310. This operates servo devices 375 and 376(FIG. 14) and 380 (FIG. 16) to provide the radial arm-lengthcompensating transmission. Finally, rod 374 provides a mechanicalfeedback connection to maintain parallelism between arm 16' of apparatus10b and arm 324 of mechanism 310. This arrangement is part of the meansfor operating servo torque transmitter 338 (FIG. 14) that provides theelevation-compensating signal.

The entire mechanism 310, said to be half-scale compared to the lengthof arm 16, 38a, could be made fullscale, as by using arm 16 itself inplace of the described arm 324; and in that case, there would be no needfor the feed-back connections since the compensation signal generatingmechanism would then be directly integrated in the head-carryingapparatus.

The accommodation provided by signals from mechanism 310 to adapt theprimary motions of azimuth, radial arm length and angular elevation tothe conveyor-carried article are also useful for adapting the secondarymotions of tilt and swing of work head 18a to the conveyor movement. Tothis end, the tilt and swing of work head 18a is operated by the sameencoders and off-set servo torque receivers as in FIGS. 1-4, with signalinput from servo torque transmitters 338 and 346. The connections to theoff-set servo torque receivers for adjusting the tilt and swing of workhead 18a are those to produce equal and opposite compensation angles inrelation to the compensation angles of the elevation of arm 16' and ofthe rotation of post 14'. For example, if the conveyor motion shouldnecessitate lowering of arm 16' in FIG. 12 toward the horizontal, thenwork head 18a is to be tilted upward by an equal and opposite angle inorder to maintain the attitude of work head 18a constant in space. Theattitude of work head 18a is basically a program-controlled mo- Themechanism 310 of FIG. 12 isdescribed above in connection with the use ofapparatus 10b with a conveyor. However, it is readily possible to takeadvantage of some characteristics of this apparatus even, ifthere wereno conveyor present. For example, the mechanism3-10adapts the rest ofapparatus 10b to straight-line motion in one direction by providinginput to motor 330. Consequently, in case straight-line motion iswanted, suitable input to this motor will produce linear traversemotions of work head 18a. Further, if uniform advances'are wanted alongthis line from each position to the next, as in loading a pallet, thenrepeated equal increments to this motor 330 will produce the desiredequal linear displacements of work head 18a. These increments can evenbe provided under program control, as by making motor 330 part of adigital servo system controlled by the recorded program. Motor 330 maytake the form of a pulse-counting motor, advancing one small butaccurate step in response to each pulse and supplied with trains ofequal numbers of pulses for successive equal steps of head 18 along aline parallel to shaft 322. Successive operations may then be carriedout by work head 18a at regular-spaced locations on one or more articlesalong the line without the necessity of manipulating the manual controlsof the apparatus in the teach or program-recording mode, for each suchlocation.

The apparatus 10b of FIG. 12 is readily capable of operating between themoving conveyor and a stationary location in alternate operations,merely by incorporating the mechanism of FIG. 11 in eachoif-set-introducing and position-encoding assembly in the same manner asalready described in connection with FIG. 11.

In both of the embodiments, those of FIGS. 6 and 12, the pivot 16a ofarm 16 and the longitudinal axis of arm 16 lie in a common plane. It isunderstood that the invention applies to equivalent apparatus. Forexample, there is a commercial program-controlled apparatus very similarto those illustrated in the drawings, having an arm like arm 16 hereinwhose longitudinal axis, when horizontal, extends along a line that islocated a small but sometimes significant distance above the pivotcorresponding to pivot 16a herein. This does not upset the functioningof either apparatus, provided that the manipulators 196 and 310 havecorresponding configurations.

FIG. 4C shows a means for introducing a digital-value olf-set betweenthe control information supplied by the program recording and thehydraulic actuator-and-controlvalve system that responds to the inputcontrol information. In like manner, the apparatus of FIGS. 6-9 and thatof FIGS. 1216' may be equipped with three digital encoders representingthe three oiT-sets to be provided, in the arm length, in the elevationand in the azimuth angle. Thus, in the embodiment of FIG. 12, unit 380(FIG. 16), unit 338 (FIG. 13), and unit 346 may be replaced by digitalencoders whose output may be introduced between the several encoders294, 292 and 290 and their respec tive information input registerscomparable to the encoder 104, the input register 104a and the off-setintroduction unit 108' in FIG. 4C. The same feature may be used toadvantage in the apparatus of FIGS. 6 and 7. Thus, servo receiver 226and ditferential 228 which introduce an oil"- set between encoder 224and the program drum may be replaced by the digital oif-set introducingarrangement in FIG. 4C.

The embodiments of FIGS. 6 and 12 involve a preferred form of controlmeans for each of the actuators, e.g. actuators 20, 34 and 38. However,in accordance with more general aspects of the invention, other forms ofactuators may be substituted, such as that in application Ser. No.686,111, filed Nov. 28, 1967, by George C. Devol, and in that case onceagain, the off-set information may be generated by mechanisms shownherein, using off-set digital encoders in lieu of the servo transmittersin FIGS. 13- 15 for example, and combining the data from these encoderswith the primary data furnished by the primary source of controlinformation, in the manner of FIG. 11.

A wide latitude of further variation and varied application of the novelfeatures of the invention will be readily devised by those skilled inthe art, based on the foregoing. Consequently, the invention should beconstrued broadly in accordance with its full spirit and scope.

We claim:

1. Apparatus for moving a workhead through a pattern of motions,including an arm operable arcuately about a first axis, said arm havinga lengthwise movable part adapting the arm to be extended and retracted,said lengthwise movable part carrying said workhead, a first angularactuator for operating said arm about said first axis and a lengthwiseactuator for extending and retracting said lengthwise movable part ofsaid arm, and control apparatus for said actuators, said controlapparatus including control means individual to said actuators,respectively, a linear-motion control for providing control inputrepresenting motion of said workhead along a path requiring lengthwiseadjustment of said arm and angular motion of said arm, andrectilinear-to-polar converter means in at least partial control of bothsaid individual control means and responsive to said linear-motioncontrol for imparting a linear component of motion to the workhead.

2. Apparatus in accordance with claim 1, wherein said control apparatusincludes a main source of motion control information for producing asequence of motions of the workhead and separate means for providingcontrol information to said linear motion control, for effecting apattern of motions of said workhead as directed by the main source ofmotion control information, modified in accordance with thelinear-motion control information.

3. Apparatus in accordance with claim 1, wherein said control apparatusincludes a main source of motion control information to respective onesof said individual control means for producing a sequence of motions ofthe workhead, offset coupling means in each of said individual controlmeans controlled by said rectilinear-to-polar converter, and separatemeans for providing control information to said linear motion control,for effecting a pattern of motions as directed by the main source ofmotion control information, modified in accordance with linearmotioncontrol information.

4. Apparatus in accordance with claim 1, including a second linearmotion control, said rectilinear-to-polar converter means includingportions operable at right angles to each other, said portions beingresponsive to said linearmotion controls, respectively, and a mainsource of motion control information for said linear-motion controls foroperating said converter means to impart controlled sequences of motionin at least two dimensions to said work head.

5. Apparatus in accordance with claim 4, further including means forimposing offset motion control information on one of said linear motioncontrols, so that said workhead is operable through motions inaccordance with said main source of motion control information asmodified by the offset information means.

6. Apparatus in accordance with claim 1, wherein said arm is operable ina coordinate additional to said lengthwise and angular motions so as tocarry said workhead through three-dimensional paths, and including anadditional actuator and individual control means for said additionalactuator.

7. Apparatus in accordance with claim 3, wherein said arm is operable ina coordinate additional to said lengthwise and angular motions so as tocarry said workhead head through three-dimensional paths, and includingan additional actuator and individual control means for said additionalactuator responsive to said main source of information and to saidconverter means.

8. Apparatus in accordance with claim 6, including two additionallinear-motion controls in control of said converter means, saidconverter means including three elements operable at right angles toeach other in accordance with said three linear-motion controls,respectively, and a main source of motion control information for saidlinearmotion controls for operating said converter means to impartcontrolled sequences of motion in three dimensions to said workhead.

9. Apparatus in accordance with claim 8, further including means forimposing offset motion control information on one of said linear motioncontrols, so that said workhead is operable through motions inaccordance with said main source of motion control information asmodified by the offset information means.

10. Apparatus in accordance with claim 1, wherein said arm is operableabout a second axis at right angles to said first axis, and including asecond angular actuator and individual control means for said actuatorat least partially controlled by said converter means.

11. Apparatus in accordance with claim 1, wherein said arm is operableabout asecond axis at right angles to said first axis, and including asecond angular actuator and individual control means for said actuatorat least partially controlled by said converter means, and wherein saidcontrol apparatus includes a main source of motion control informationto respective ones of said individual control means for producing asequence of motions of the workhead, offset coupling means in each ofsaid individual control means controlled by said converter means, andseparate means for providing control information to said linear motioncontrol, for effecting a pattern of motions as directed by the mainsource of motion control information, modified in accordance with thelinear-motion control information.

12. Apparatus in accordance with claim 1, wherein said arm is operableabout a second axis at right angles to said first axis, and including asecond angular actuator and individual control means for said secondangular actuator at least partially controlled by said converter means,said converter means including three portions operable rectilinearly inaccordance with the three linear-motion controls respectively, saidportions being operable at right angles to each other, and a main sourceof motion control information for said linear-motion controls foroperating said converter means to impart controlled sequences of motionin three'dimensions to said workhead.

13. Apparatus in accordance with claim 12, further including means forimposing offset motion control information on one of said linear motioncontrols, so that said workhead is operable through motions inaccordance with said main source of motion control information asmodified by the offset information means.

14. Apparatus in accordance with claim 1, wherein said converter meansincludes first and second levers operable about a main lever axis, athird level parallel to said first lever and operable about another axisparallel to said main lever axis, a rod carried by said first and thirdlevers at equal distances from said axes thereof, said second leverhaving an operative part on and adjustable along said rod to move therod to various angles in relation to said first lever and to variousdistances from said main lever axis, said linear-motion control beingarranged to determine the position of said operative part of the secondlever along said rod, means enforcing conjoint angular motions of saidarm and said second lever, means for maintaining a constant ratiobetween the lengths of said arm and said second lever, and meansresponsive to the angular displacement between said first and secondlevers for at least partially controlling the individual control meansof said first angular actuator.

15. Apparatus in accordance with claim 14, wherein each of saidindividual control means includes first and second control elements, andwherein said control apparatus includes a main source of controlinformation for respective ones of said first control elements forproducing a sequence of motions of the workhead and wherein said secondcontrol elements in said individual control means form respectiveportions of said means enforcing conjoint angular motions of the secondlever and said arm and

